HVAC Load Calculations

Using Load Calculations to determine the size of your HVAC Design

For anyone who is building a new home or looking to upgrade the energy efficiency of their existing home, the first place to start is with the HVAC System. The HVAC design and system also plays a factor in the home’s renovation or building costs, as well as comfortability, reliability and air quality, just to name a few characteristics. Having accurate load calculations will predicate the size and design of the home’s HVAC system. Therefore, getting precise heating and cooling load calculations is a vital step, as the HVAC System represents the heart of a home.

Getting the wrong HVAC System calculations can result in an off-sized system, as well as working the unit to excess. This can make it loud and unbearable, but it can also deter a homeowner’s ability to maintain a congruous and comfortable indoor climate. Aside from energy wastefulness, inability to dictate the moisture and keep allergens away, these circumstances may also cause the HVAC System to break.

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The Importance of Choosing the Best HVAC System Size

You may wonder why it is so critical to run these calculations and obtain the most formal calculations for the home’s heating and cooling needs, since guessing has served you well in the past. However, the last decade has seen rising code requirements throughout the United States; with the trend expected to continue. Therefore, the methods of calculating the optimal energy system must evolve with these changes.

For example, increased gas, oil and alternative fuel prices have continued rising, which has caused more homeowners to tighten up and improve their homes with insulation upgrades, better windows, and other energy improvements. This equates to less strain and overload on the HVAC system; and with better air quality and comfort throughout the home. Once the insulation and air tightness levels rise, the system’s peak cooling or heating load lessens. Therefore, the more energy consumed by the home, the smaller size its heating and cooling loads will be. That is why even HVAC experts can no longer “guess” the best size unit.

How to Determine the Optimal HVAC System Size

Configuring a home’s energy use capacity depends on several variables, including the size of the home, climate zone, U-value of the windows, directional orientation, and tightness of the structure, among other characteristics. The many scenarios encountered by HVAC designers can be confusing, at least without some guidance. The precision of the estimate depends upon getting these details as accurate as possible.

For example, many issues can affect the performance load calculations, both for homes needing energy upgrades, as well as new home constructions. Even external factors, like the year-round climate of the region, can make an impact on the estimate.

Several primary factors are to be considered when calculating HVAC system capabilities. You must address these three components:

Physical attributes: These include the design and layout of the home, location, internal and external conditions (such as directional orientation, humidity levels, elevation, etc.). Rarely will two homes will have the same calculations, regardless of the square footage or climate, or even the same blueprint. These are not the only characteristics to consider. Solar energy also plays a role to consider the optimal heating or cooling capability.

Insulation values: Older homes may be drafty, while newer homes may be adequately insulated. A home’s thermal enclosures should also be counted in the calculations, such as door and window air tightness, shading and proximity to sunlight. Bigger windows may provide more solar energy, so it is important to consider the thermal conductivity and solar efficiency. Depending on how sealed the home is; the less energy it may need in its HVAC design.

Living factors: A home with six people naturally uses more energy than one with just one couple or single person living in it, therefore this must also be considered. How much power does each person use (i.e. – showers, electronics, appliances, lighting)? What temperature do the occupants typically keep their settings on? And does the home feature an attic or basement? Consider these details about the interior workings of the HVAC system.

There is software available to help determine these calculations. It prompts users to answer a series of questions that takes the guessing out of choosing the best HVAC size. However, Comfort First does provide load calculations with each new installation. Remember, accuracy is imperative to ensure maximum efficiency in airflow, equipment size and capability. All the designs will be for naught if this one detail is not precise.

Things to Watch Out for When Calculating a Home’s HVAC System

Avoid overestimating the HVAC load calculations, because it can result in either overload or overworking the system. Contrary to a widespread misconception, it is not better to increase the size of the system ‘just in case’, because the unit must run continuously to meet the demands of the home. Therefore, short-cycling of a system can result in more wear and tear of the HVAC unit, leading to potential breakdowns. It is also more of an energy waster, resulting in higher energy bills and wastefulness of resources.

As if these reasons weren’t good enough, there may be other problems in choosing the wrong sized HVAC system. If the home does not stay at the same temperature consistently, it makes inhabitants uncomfortable, causing frequent thermostat changes. Moisture in the air can become a breeding ground for mold. These and many more problems are the result of improper HVAC system designs.

When building a new home, it is important to think ahead. Get the right specifications to avoid future issues with the heating and cooling. Our expert HVAC designers, techs and installers can help you every step of the way. We handle remodels and upgrades, too. Contact us for assistance in choosing the best HVAC design for your property.